1. Field of the Invention
The present invention is generally related to a direct fuel injection system for a two cycle internal combustion engine and, more particularly, to a means for facilitating the starting of the engine with a stratified charge.
2. Description of the Prior Art
Direct fuel injection (DFI) engines are well known to those skilled in the art. Engines of this type incorporate a fuel injector that is able to inject a fuel/air mixture into the combustion chamber of the engine when the piston is moving upwardly toward its top dead center (TDC) position. Many techniques for controlling the fueling procedures of the engine are also well known.
U.S. Pat. No. 5,913,302, which issued to Ruman et al on Jun. 22, 1999, discloses an ignition coil dwell time control system. A two stroke injected internal combustion engine has an ignition coil dwell time control system. An electronic control unit controls switching of electronic ignition coil drivers in a manner to minimize ignition coil dwell times at medium and high engine speeds where low ignition coil dwell times can be used without sacrificing engine performance. The electronic control unit also implements an intermittent spark plug cleaning strategy to remove carbon deposits from fouled spark plugs. Intermittent cleaning is accomplished during engine operation by periodically raising the ignition coil dwell time to an exaggerated cleaning level for a relatively short period of time (e.g. one minute) after it is determined the spark plug cleaning should occur (e.g. 10 to 20 engine operating hours since previous cleaning).
U.S. Pat. No. 5,848,582, which issued to Ehlers et al on Dec. 15, 1998, discloses an internal combustion engine with barometric pressure related start of air compensation for a fuel injector. A control system for a fuel injector system for an internal combustion engine is provided with a method by which the magnitude of the start of air point for the injector system is modified according to the barometric pressure measured in a region surrounding the engine. This offset, or modification, of the start of air point adjusts the timing of the fuel injector system to suit different altitudes at which the engine may be operating.
U.S. Pat. No. 6,161,527, which issued to Ruman on Dec. 19, 2000, discloses an air assisted direct fuel injection system. The system incorporates a plurality of fuel injection arrangements, wherein each fuel injection is associated with a particular cylinder of the engine. Each of the fuel injection arrangements comprises a fluid passageway in which fuel and air are combined prior to injection into a combustion chamber of the cylinder. A valve is movable with respect to an injection port to allow the pressurized fuel/air mixture to flow from the fluid passageway into the combustion chamber. A fuel injector is used to inject liquid fuel into the fluid passageway to be combined with pressurized air within the passageway. The system has a common air rail and a common fuel rail which are each connected to a plurality of fuel injection arrangements. Upward movement of a piston within the cylinder is used to pressurize the air within the common air rail. All of the fuel injection arrangements can be used to contribute pressurized air to the common air rail.
U.S. Pat. No. 5,924,404, which issued to Ruman et al on Jul. 20, 1999, discloses a cylinder-specific spark ignition control system for direct fuel injected two stroke engine. A direct fuel injected two stroke engine controls spark ignition timing and/or ignition coil dwell time on a cylinder-specific basis. The engine also preferably controls fuel injection timing and amount and injection/delivery duration on a cylinder-specific basis. Cylinder-specific customization of spark ignition and fuel injection allows better coordination of spark with fuel injection which results in better running quality, lower emissions, etc. Memory in the electronic control unit for the engine preferably includes a high resolution global look-up table that determines global values for spark ignition and fuel injection control bases on engine load and engine speed. Memory in the electronic control unit also includes a plurality of low resolution, cylinder-specific offset value look-up tables from which cylinder-specific offset values for spark ignition and fuel injection can be determined, preferably depending on engine load and engine speed. The offset values are combined with the global values to generate cylinder-specific control signals for spark ignition and fuel injection.
U.S. Pat. No. 6,298,824, which issued to Suhre on Oct. 9, 2001, discloses an engine control system using an air and fuel control strategy based on torque demand. The control system for a fuel injected engine provides an engine control unit that receives signals from a throttle handle that is manually manipulated by an operator of a marine vessel. The engine control unit also measures engine speed and various other parameters, such as manifold absolute pressure, temperature, barometric pressure, and throttle position. The engine control unit controls the timing of fuel injectors and the injection system and also controls the position of a throttle plate. No direct connection is provided between a manually manipulated throttle handle and the throttle plate. All operating parameters are either calculated as a function of ambient conditions or determined by selecting parameters from matrices which allow the engine control unit to set the operating parameters as a function of engine speed and torque demand, as represented by the position of the throttle handle.
U.S. Pat. No. 6,145,490, which issued to Heidenfelder et al on Nov. 14, 2000, describes a method for operating a direct injection internal combustion engine during starting. A changeover is made between a so-called low-pressure starting with a homogeneous mixture and a so-called high pressure starting with a stratified mixture as a function of an engine coolant temperature. Since, during the high-pressure starting of the internal combustion engine, injection is released only when a pressure in a high-pressure accumulator exceeds a predetermined threshold value, the injected fuel is better prepared. During such high-pressure starting, injection is predetermined by an injection quantity and an angle of the end of injection. Predetermining the angle of the end of injection, in contrast to predetermining an angle of commencement of injection during conventional low-pressure starting, ensures that there is an ignitable mixture present at the sparkplug, specifically irrespective of duration of injection.
U.S. Pat. No. 6,058,906, which issued to Yoshino on May 9, 2000, describes a fuel/air ratio control for an internal combustion engine. An engine system for an internal combustion engine of a type having a stratified combustion mode and a homogenous combustion mode comprises a controller for increasing a fuel air ratio (or equivalence ratio) of an air fuel mixture produced in the engine abruptly in a transient state during transition from the stratified mode to the homogenous mode to ensure stable combustion. The controller estimates a residual EGR gas quantity, and produces a step change in the fuel air ratio when the fuel air ratio enters a predetermined unstable range and the EGR gas still remains in a considerable amount.
U.S. Pat. No. 5,964,199, which issued to Atago et al on Oct. 12, 1999, describes a direct injection system internal combustion engine cont apparatus. In a direct injection internal combustion engine, a stratification combustion condition, a homogenous combustion condition and an intermediate combustion condition, which is intermediate the stratification combustion and the homogenous combustion conditions, are controlled selectively according to an operation condition of at least one selected from a combustion condition, an output condition of the engine and an acceleration condition of a vehicle. Without defeating an intended low fuel consumption operation, the engine operates to obtain a reduction of harmful exhaust gas. As a result, by assuring the low fuel consumption operation, an improvement in combustion stability and smoke reduction can both be realized.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Certain internal combustion engines occasionally exhibit certain disadvantageous starting characteristics that can be exacerbated by the use of a homogenous charge during starting procedures. Particularly when the cylinder walls are cold, as a result of the engine being inoperative for a period of time, a homogenous charge can result in the wetting of the cylinder walls when the fuel vapor contacts those walls. The fuel vapor condenses on the cylinder walls and creates a condition in which it is difficult to vaporize the condensed fuel within the combustion chamber. This condition can be further exacerbated by the inherent variability in airflow during the initial movement of the pistons within the cylinders of the engine. It would therefore be significantly beneficial if a method for starting an internal combustion engine could be improved in such a way that reduces the wetting of the cylinder walls with fuel vapor, provides a stratified rather than a homogeneous charge, and compensates for the variability of airflow during the initial movement of the pistons within the cylinders of an internal combustion engine.
A method for controlling the operation of an internal combustion engine during starting, in accordance with the preferred embodiment of the present invention, comprises the steps of providing a fuel injector for injecting fuel into a combustion chamber within a cylinder of the internal combustion engine and providing an igniting device for igniting the fuel in the combustion chamber. It also comprises the steps of determining when the internal combustion engine is being started subsequent to the engine being inoperative for a preselected period of time and measuring a position of a piston within the cylinder. It comprises the steps of causing the fuel injector to inject fuel into the combustion chamber when the piston is at a first position within the cylinder and subsequently activating the igniting device when the piston is at a second position within the cylinder, wherein the first and second positions in one embodiment of the present invention are within 10xc2x0 to 20xc2x0 of crankshaft rotation of each other in relation to the rotational position of the crankshaft of the internal combustion engine.
In an alternative embodiment of the present invention, the first and second piston positions can be within 12xc2x0 of each other in relation to the rotation position of a crankcase of the internal combustion engine. In a most preferred embodiment of the present invention, the first and second positions are generally 15xc2x0 apart in relation to the rotational position of the crankshaft. The first position occurs between 45xc2x0 and 55xc2x0 before top dead center (BTDC) in relation to the rotational position of the crankshaft and the second position occurs between 30xc2x0 and 40xc2x0 before top dead center (BTDC) in relation to the rotational position of the crankshaft.
The activating step occurs when a fuel mixture injected by the fuel injector is stratified. In other words, a spark plug is activated before the fuel mixture has an opportunity to become homogenous. The position of the piston within the cylinder is determined relative to its top dead center (TDC) position, when the piston is at its maximum degree of travel in a direction toward the combustion chamber. The determining step comprises the step of either monitoring a manually operable start switch or measuring an operating speed of the internal combustion engine and comparing the operating speed to a threshold speed magnitude. The internal combustion engine is a direct fuel injected two cycle engine.